Securing of a telecommunication device equipped with a near-field communication module

ABSTRACT

A telecommunication device including a battery capable of providing a first power supply voltage to circuits of the device, among which at least one security module; a near-field communication module capable of providing a second power supply voltage to the security module; and a circuit for activating the provision of the second power supply voltage, including a switch controllable at least by one element accessible from outside of the device.

FIELD OF THE INVENTION

The present invention generally relates to mobile telecommunicationdevices equipped with a near field communication circuit (NFC).

DISCUSSION OF PRIOR ART

Cell phones are more and more often equipped with a near fieldcommunication interface, which enables combining electromagnetictransponder functions with mobile telephony functions. In particular,this adds contactless card type electromagnetic transponder emulationfunctions to the mobile telecommunication device, of personal digitalassistant, cell phone, smartphone, or other type. This enriches thefeatures of the mobile device, which can then be used, for example, asan electronic purse, as a debit or credit system, as an accessvalidation device, as a transport ticket, etc.

To emulate the operation of a contactless chip card, the mobiletelecommunication device is equipped with a contactless front-endintegrated circuit (CLF), also called NFC router. This router isequipped with a radio frequency transceiver front head associated with alow-range antenna to communicate like an electromagnetic transponder.The router uses the capacities of the mobile device processor(s) fordata processing and storage operations. For access control, electronicpurse, payment, and other applications, a secure element enabling toauthenticate the user is used. This secure element is either integratedto the mobile telecommunication device (dedicated integrated circuit,circuit welded to the printed circuit board) or contained in amicrocircuit supported by a subscriber identification module (SIM), orany other removable card, for example in the standard format of a memorycard,

A specificity of such a mobile telecommunication device is that it iscapable of operating in NFC when it is off or, more generally, when itscircuits are not powered by the battery or another power supply elementof the mobile device.

In this case, the NFC router draws the power necessary to its operation,like an electromagnetic transponder, from the field radiated by a nearbyterminal. It then provides the power supply necessary to the securitymodule circuits to validate near-field transactions.

When the device is powered by its batter y and its internal circuits areoperating, different security mechanisms may be implemented, forexample, to avoid a hacking of the SIM card. However, when the device isonly powered via the NFC router, such mechanisms cannot be implemented.This is a weakness of such a mobile telecommunication device.

SUMMARY

An object of the present invention is to overcome all or part of thedisadvantages of mobile telecommunication devices associated with anear-field transmission module.

Another object of an embodiment of the present invention is to improvethe security against a hacking attempt when the device is only poweredby its near-field transmission module.

Another object of an embodiment of the present invention is to provide asolution compatible with usual subscriber identification modules.

To achieve all or part of these and other objects, the present inventionprovides a telecommunication device comprising:

-   -   a battery capable of providing a first power supply voltage to        circuits of the device, among which at least one security        module;    -   a near-field communication module capable of providing a second        power supply voltage to the security module; and    -   a circuit for activating the provision of the second power        supply voltage, comprising a switch controllable at least by one        element accessible from the outside of the device.

According to an embodiment of the present invention, said switch is amechanical switch.

According to an embodiment of the present invention, said switch is anelectronic switch controlled by at least one signal having its stateconditioned at least by that of said control element.

According to an embodiment of the present invention, the electronicswitch can be actuated both when the device is powered by the firstvoltage and when it is powered by the second voltage.

According to an embodiment of the present invention, said switch iscapable of short-circuiting two conductors for providing said secondpower supply voltage.

According to an embodiment of the present invention, said switch is onin the idle state.

According to an embodiment of the present invention, said switch is inseries with a current-to-voltage conversion element, a signal indicativeof the state of the switch being sampled from the junction point ofthese components towards the near-field communication module.

The present invention also provides a method for controlling anear-field communication module, wherein a response to a requestoriginating from a terminal having the device in its field is onlyauthorized if the switch is off.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of the presentinvention will be discussed in detail in the following non-limitingdescription of specific embodiments in connection with the accompanyingdrawings.

FIG. 1 very schematically shows a mobile telecommunication device of thetype to which the present invention applies as an example and itssurrounding system;

FIG. 2 is a block diagram illustrating the power supply of the circuitsinternal to the telecommunication device;

FIG. 3 very schematically shows an embodiment of a circuit for securinga security module;

FIG. 4 very schematically shows an embodiment of a mobiletelecommunication device equipped with the circuit of FIG. 3;

FIG. 5 is a block diagram of a variation of the circuit of FIG. 3; and

FIG. 6 schematically illustrates an example of exchanges between areader, a router, and a security module.

DETAILED DESCRIPTION

The same elements have been designated with the same reference numeralsin the different drawings. For clarity, only those elements and stepswhich are useful to the understanding of the present invention have beenshown and will be described. In particular, the coding and communicationprotocols, be it for near-field transmissions or for telecommunicationsin GSM mode, have not been detailed, the described embodiments beingcompatible with usual protocols. Further, the circuits forming themobile communication device have not been detailed either, the describedembodiments being here again compatible with usual devices.

The embodiments will be described in relation with a cell phone. Theyhowever more generally apply to any telecommunication device adapted toa mobile network (for example, Wifi, Bluetooth, WiMax, etc.) andassociated with a contactless near-field transmission module.

FIG. 1 very schematically shows a mobile telecommunication device 1 (forexample, a cell phone).

Device 1 comprises a central processing unit 12 (CPU/TH) formed of atleast one microprocessor forming the device core. This microprocessor ispresently called a terminal host. For the telecommunication operationover a network (GSM, 3G, UMTS, etc.), this microprocessor usesidentification and authentication data provided by a subscriberidentification module 14 (SIM), forming a security module of the device.Microprocessor 12 is capable of using one or several internal memories(not shown) of the telephone. The different elements of interface withthe user (keyboard, display, speaker, etc.) have not been shown.

The mobile devices to which the described embodiments apply combine thetelecommunication function with that of a near-field contactlesstransmission system. To achieve this, device 1 comprises a circuit 18(CLF) forming a near-field communication module, like an electromagnetictransponder. Module 18 is associated with an antenna 182 distinct froman antenna 20 intended for the mobile telephony network. The near-fieldcommunication module will be called “NFC router” since it generallyintegrates all the functions useful to the emulation of a contactlesscard within a same circuit, but the described embodiments apply to anyNFC-type module.

The different elements of device 1 communicate according to variousprotocols. For example, circuits 12 and 18 communicate over a link 1218of I2C, SPI, or other type, and SIM card 14 communicates withmicroprocessor 12 over a link 1214 according to ISO standard 7816-3.Router 18 communicates with the SIM card, for example, over asingle-wire bus 1418 (SWP—Single Wire Protocol). Other versions ofprotocols and links are of course possible.

As illustrated in FIG. 1, device 1 is capable of communicating over atelecommunication network (for example, GSM) symbolized by a relayantenna 3, for example, with another mobile device P. In near field, theCLF router is capable of communicating with a reader 5 (READER), forexample, an NFC terminal or any other contactless communicationterminal.

FIG. 2 is a block diagram illustrating the power supply of the differentcircuits of mobile device 1.

The device generally comprises a battery 16 or a power supply capable ofproviding (generally via a voltage regulator, not shown) a voltage VCCto the different electronic circuits and in particular to NFC router 18,to SIM card 14 (or other security module), to central processing unit12, as well as to the other circuits (not shown) of the device(keyboard, display, etc.). A switch 162 is functionally interposedbetween battery 16 and a power supply rail 164 providing voltage VCC.Switch 162, generally electronic, is controlled under the action of amechanical switch accessible by the user from outside of device 1.

When the mobile device is off (switch 162 open) or when it is in aso-called low-power operating mode (for example, at standby), NFC router18 remains capable of extracting a power supply voltage from a magneticfield (RF FIELD) radiated by a near-field communication reader (notshown in FIG. 2). Router 18 comprises power regulation means (symbolizedby a block 182-REG). Regulator 182 provides a power supply voltage NFCVCC to the different circuits of router 18 as well as, over a link 1814,to SIM card 14. This enables the router to access the security module toobtain authentication or identification elements enabling to validate atransaction with the reader, even when the other device circuits are notpowered.

FIG. 3 schematically shows an embodiment of a circuit 6 for securing theSIM card when the telecommunication device operates in NFC mode. Circuit6 is a circuit for activating the SIM card power supply.

According to this embodiment, link 1814 between router 18 and securitymodule(s) 14 is connected to ground 166 by a switch 62. The function ofthis switch is to pull link 1814 to ground as long as a transaction isnot authorized.

Preferably, and as illustrated in FIG. 3, a resistor 64 is interposedbetween switch 62 and link 1814. Resistor 64 forms a current-to-voltageconverter and the junction point of the resistor and of switch 62 isconnected, by a link 66, to a gate of router 18. The signal present overlink 66 indicates, by its state, the state of switch 62, and thus theauthorization or not of a near-field operation. Router 18 can use thisinformation to enable/disable some of its internal functions. Forexample, the router is only authorized to respond to a request from thereader when this signal is active.

In the idle state, switch 62 is on. This means that, by default, thesecurity module is not powered by router 18, even if the lattergenerates a voltage NFC VCC.

FIG. 4 schematically shows a device 1 equipped with the system of FIG.3. According to this embodiment, switch 62 is mechanical and can beactuated by a push-button 68 accessible from outside of the device.Accordingly, a near-field transaction is only authorized when the userpresses push-button 68.

FIG. 5 shows another embodiment according to which switch 62 is anelectronic switch. Circuit 6 receives a signal 682 transmitting thestate of push-button 68 and a control signal CT that comes from anotherexternal authorization element when the device is powered by itsbattery. This embodiment enables to take advantage of the protectionfunction (near-field transaction authorization) in all device powersupply modes. For example, signal CT is controlled, when the device isactive (powered by the battery), by an action of the user on a key ofthe keyboard or on an area of a touch screen.

FIG. 6 schematically illustrates an example of exchanges between reader5, router 18, and the SIM card.

When the device enters field RF FIELD of the reader and it is notpowered by its battery, the router detects the presence of the magneticfield (IN RF FIELD). It then transmits a control signal (EVT_FIELD_ON)to card 14 to indicate this event. The reader periodically sendsrequests to the possible routers in its field. When the router receivesa request, if the state of signal 66 indicates an authorization (OK),the router responds (ATQ) to the reader. Otherwise, the router remainsmute (MUTE) as long as such an authorization has not been received.Then, an anti-collision procedure is implemented between the reader andthe router. Then, the router activates the SIM card with a controlsignal EVT_CARD_ACTIVATED. The card and the reader then communicate(EVT_SEND_DATA) via the router.

In its simplified embodiment (with no link 66), the implementation isparticularly simple. It is sufficient to add to the device a switchshort-circuiting by default power supply voltage NFC VCC (connectinglink 1814 to ground) and to provide an actuator 68 accessible fromoutside of the mobile device.

It should be noted that the described embodiments require nomodification of the SIM card.

Various embodiments have been described, various alterations andmodifications will occur to those skilled in the art. For example,switch 62 may be interposed on link 1814 and is then off in the idlestate. However, the embodiment illustrated by FIG. 3 eases theextraction of a state signal towards the NFC router.

1. A telecommunication device comprising: a battery capable of providinga first power supply voltage to circuits of the device, among which atleast one security module; a near-field communication module capable ofproviding a second power supply voltage to the security module; and acircuit for activating the provision of the second power supply voltage,comprising a switch controllable at least by one element accessible fromthe outside of the device.
 2. The device of claim 1, wherein said switchis a mechanical switch.
 3. The device of claim 1, wherein said switch isan electronic switch controlled by at least one signal having its stateconditioned at least by that of said control element.
 4. The device ofclaim 3, wherein the electronic switch can be actuated both when thedevice is powered by the first voltage and when it is powered by thesecond voltage.
 5. The device of claim 1, wherein said switch is capableof short-circuiting two conductors for providing said second powersupply voltage.
 6. The device of claim 5, wherein said switch is on inthe idle state.
 7. The device of claim 5, wherein said switch is inseries with a current-to-voltage conversion element, a signal indicativeof the state of the switch being sampled from the junction point ofthese components towards the near-field communication module.
 8. Amethod for controlling a near-field communication module of the deviceof claim 7, wherein a response to a request originating from a terminalhaving the device in its field is only authorized if the switch is off.